Vitrifiable photosensitive emulsion



United States Patent O 3,406,066 VITRIFIABLE PHOTQSENSITIVE EMULSIONFrancis J. Avery, Vestal, N.Y., assignor to GAF Corporation, acorporation of Delaware No Drawing. Filed Apr. 30, 1964, Ser. No.363,982 13 Claims. (Cl. 9634) ABSTRACT OF THE DISCLOSURE Photosensitiveemulsion layers on a refractory surface, adapted for vitrification whileresisting contraction, stretching, blistering, tearing and frilling,containing to 50% of polyacrylamide or acrylamide-acrylic acidcopolymer, or in the case of silver halide gelatin emulsions, containing1.25 to 3.75 parts of silver per part of gelatin; and a method ofproducing vitreous colored images therewith involving imagewise exposureof such silver halide emulsions, developing, converting the image tometal ferrocyanide(s) which yield a colored oxide on firing, and firingthe image.

The present invention relates to photosensitive hydrophilic emulsionlayers capable of being subjected to a vitrification process withoutcausing the emulsion layer to exhibit such defects as contraction,stretching, blistering, tearing or frilling during a firing process inwhich all of the organic matter is consumed. More particularly, theinvention pertains to gelatino-silver halide emulsions containing lessgelatin than is normally present in such silver halide emulsions andwhich are especially applicable to the formation of permanent vitrifiedimages on refractory surfaces and to a method of using the silver imageproduced from such emulsions to supply the ceramic pigment and fluxneeded for formation of said vitrified image.

The prior art has indicated that it is necessary to use collodionemulsions for producing vitrified photographic images since thecarbonaceous ash residue formed while firing a normal gelatino-silverhalide emulsion causes contraction, streaching, blistering, tearing orfrilling of the emulsion layer.

I have discovered, contrary to the fixed notion of the prior art, thatgelatino-silver halide emulsions may be used to form excellent permanentvitrified photographic images on refractory surfaces providing that thequantity of gelatin in such gelatino-silver halide emulsion is reducedbelow that usually present in silver halide emulsions and bears a ratioto the weight of silver in such emulsion of silver/ gelatin by weightranges from 3.75/1 to 1.25/1.

I have also discovered that the silver image formed by the usualphotographic process from such silver halide emulsions is uniquelyadapted to a conversion method leading to the imagewise formation of alead sulfate flux and a ferrocyanide of a base metal yielding theceramic pigment on firing.

The employment of such emulsions for such purpose and their processingto produce such ceramic pigment and flux constitute, in part, theobjects of my invention.

The radiation-sensitive halide employed in the emulsions may be anysilver halide generally used in forming photographic emulsions, such assilver bromide, silver chloride, silver chlorobromide, silverbromoiodide, silver chlorobromide iodide, or the like. The silver halidese lected while observing the noted ratio of silver to gelatin, however,must be such that the resulting emulsion has satisfactory speed,preferably that of enlarging paper. Such emulsion, when coated on arefractory surface, may be used with any photoenlarger to produceenlarged pictures directly on such surface. Exposures for a normalnegative at three times enlargement may be at 116 for 10 to 40 seconds.This is in sharp contrast to colloidion F ice emulsions which are of avery low photographic sensitivity and require are light exposures.

While, for best results, I prefer to use the aforesaid silver halideemulsions, I find that damage to the photo sensitive emulsions may beavoided by employing. a photosensitive hydrophilic emulsion, thecolloidal carrier of which is combined with a polyacrylamide, such asthe homopolymer; a copolymer of acrylamide and acrylic acid, or amixture of the homopolymer and copolymer. The colloidal carrier orbinding agent for these photosensitive emulsions may be gelatin, gumarabic, or egg albumen, and the carrier may be sensitized with asubstance which hardens the colloid upon exposure to light or may be asilver halide. Suitable sensitizers which harden colloids, such asgelatin, on exposure to light are the bichromates and certain diazocompounds as described in Charlton, US. Patent 2,900,255.

If the photosensitive emulsion be a silver halide, it may be processedby conventional procedure, by tanning development as in Yackel, U.S.Patent 2,607,683, or by a tanning bleach as in the carbro process.Despite the sensitizer or the mode of processing, however, thephotosensitive hydrophilic emulsion must contain the polyacrylamide tobe resistant to damage on firing.

The polyacrylamide is generally present in an amount of from 10 to 50percent by weight of the colloidal carrier. The preferred polymers arethe anionic copolymer of acrylamide and acrylic acid sold by AmericanCyanamid Company under the name of Cyanamer P-26, or the polyacrylamidehomopolymer sold under the name of Cyanamer P-ZSO. Such polymers arecompatible with the colloidal carriers and mixtures thereof dry to filmsof good clarity.

The emulsions contemplated for use herein may be applied directly to arefractory permanent base by whirling, brushing, spraying, dipping, orthe like. Although the direct application is preferred, it is alsopossible to use the photosensitive emulsion in the form of a so-calledstripping film, pigment papers or transfer papers from which the imageformed thereon is subsequently transferred to the permanent base forfiring or vitrification.

The emulsions may be used for permanentizing photographic images on anyrefractory surface, such as ceramic articles, glass plates, metalplates, and enameled metal plates. These permanent images may be used toproduce reticles, record data, printed circuits, photographic picturesor designs of a decorative nature.

In addition to the photosensitive emulsion, there must also be present avitrifiable ceramic pigment and a flux. The vitrifiable pigment may beunderglaze COlOrs and stains, color glazes, overglaze colors, enamelcolors and glass colors, or even simple metal compounds, such as thecarbonates of cobalt, manganese and iron. The flux may comprise a lowmelting glass composed of lead silicates or lead borosilicates, or thelike. The flux should be compatible with the permanent base as tocoefiicient expansion and vitrification temperatures.

Underglaze colors, applied to unglazed ceramic ware, which are suitablefor use are:

Color glazes of the fritted variety which I may employ are representedby:

Glossy Black Glaze #600 Red Brown Glossy Glaze #-l0-G-179A (Both Cone 06by the above manufacturer) Overglaze colors, low melting color glassesmaturing at cone 017, which are usually applied to glazed and firedceramic ware are exemplified by:

Overglaze Brown #2210-U (Cone 017 by the above manufacturer) The ceramicpigment and flux may be added to the photosensitive emulsion,particularly when the sensitizer causes hardening on exposure to light.However, when the emulsion is a silver halide to be processed to asilver image, best results ensue when the ceramic pigment or the flux,or both, are formed imagewise through use of the silver image.

To this end, a base coated with a silver halide emulsion of the typeherein described is exposed to light underneath a pattern, developed andfixed to yield a silver image.

The silver image may then be bleached with a watersoluble ferricyanidein the presence of a salt of a heavy base metal, the oxide of which is aceramic pigment. The ferrocyanide of the heavy base metal is thenconverted to the oxide by treatment with an alkali metal hydroxide. Forexample, a silver image formed as above may be treated wtih an aqueoussolution of potassium ferricyanide and then with an aqueous solution ofmanganous sulfate. The resulting manganese ferrocyanide is converted bymeans of sodium hydroxide into manganese dioxide. The manganese dioxideimage is fired at cone 09 similar to an underglaze ceramic pigment. Theceramic base is then glazed and refired at cone O6 to yield abrownish-black image under the glaze.

Similar results are obtainable by replacing the man ganous sulfate byferric sulfate, copper sulfate, cobalt sulfate, nickel sulfate, uraniumsulfate, vanadyl sulfate, and stannous sulfate.

It is possible, however, by proper selection of the conversionconditions, to utilize the silver image to produce both the ceramicpigment and the flux. Thus a silver image formed as noted is bleachedwith a ferricyanide solution containing a salt of lead to a yellow-whitelead ferrocyanide image. The image is then treated with an acid solutionof a sulfate of a heavy base metal to form the ferrocyanide of the heavybase metal and lead sulfate.

The image is then fired and, after cooling, the plate contains avitrified positive image completely within the glaze. The decompositionof the ferrocyanide has resulted in a colored image and thedecomposition of the lead sulfate caused the image to be fluxed to aglossy vitrified surface.

By using in this procedure, for example, an acid solution of ferroussulfate for reaction with the lead ferrocyanide, there is formedimagewise a mixture of ferrous ferrocyanide and lead sulfate. Firingproduces a reddishbrown image fluxed by the lead sulfate. The ferroussulfate in this procedure may be replaced by ferric sulfate to give ablue-white image; copper sulfate, a redbrown image; manganous sulfate, ablue-white image; cobaltous sulfate, a grey-green image; nickel sulfate,a yellow-green image; uranium sulfate, a reddish image; vanadyl sulfate,a yellow image; and stannous sulfate, a white image.

The invention is further illustrated by the following examples but it isto be understood that the invention is not restricted thereto.

Example I The following solutions are made up separately:

Distilled water cc 1500 Potassium bromide gm' 80 Potassium iodide gm 1Gelatin gm 10 Distilled water cc 300 Silver nitrate gm Ammonia (28%) cc100 Dissolve each solution separately and make the emulsion under redlight illumination. At a temperature of 42 C. with rapid stirring, dumpsolution II into solution I. Digest at 42 C. for 10 minutes. Add 400 gm.of dry powdered ammonium sulfate and, with stirring, cool to 25 C. Washthe resulting precipitate three times by the process of decantation.(1000 cc. of water per wash). After the last decantation, add to theresulting sludge:

Gelatin gm 15 Potassium bromide (10%) cc 10 Allow the sludge and gelatinto soak 1 hour, then melt up with rapid stirring to a temperature of 55C. Digest for 1 hour at 55 C., then chill the resulting emulsion. Uponremelting the emulsion, it can be coated directly upon ceramic ware,glass plates, enameled metal plates, paper base or stripping film base.

At a temperature of 40 C., and with rapid stirring, add solution 11 tosolution I. Stir three minutes, then add solution III, stir threeminutes. This photosensitive material is now coated directly on aceramic base.

Example 111 The following solutions are made separately:

Gelatin gm 20 Sugar gm 5 Ceramic color glaze (Glossy Black #600) gm 10Distilled water cc Dist1lled water cc 50 Cyanamer P-26 gm 5 Distilledwater cc 50 Potassium dichromate gm 2 At a temperature of 45 C., andwith rapid stirring, add solution II to solution I. Stir for threeminutes and then add solution III, stir three minutes. Thisphotosensitive material can now be coated directly on a ceramic base.

Example IV The following solutions are made up separately:

Distilled water cc 500 Potassium bromide gm 80 Potassium iodide gm 1Gelatin gm 70 Distilled water cc 100 Silver nitrate gm 100 Ammonia (28%)cc 100 Distilled water cc 100 Cyanamer P-26 gm Cyanamer P-250 gm 1 Thisemulsion, with such normal additions as sensitizing dyes, stabilizers,wetting agents, etc., is coated directly on a ceramic base.

Example V The following solutions are made up separately:

Gum arabic gm Gelatin gm 10 Sugar gm 5 Distilled water cc 200 Distilledwater cc 200 Cyanamer P-26 gm 20 Cyanamer P-250 gm 3 (III) DistilledWater cc 50 Potassium dichromate gm 3 At a temperature of 45 C., andwith rapid stirring, add solution II to solution I. Stir for threeminutes and add solution III, stir three minutes. This photosensitivematerial can now be sprayed directly on a ceramic base.

Example VI Water cc 300 Potassium ferricyanide gm 7 Ammonia (28%) cc 7The image is washed for 5 minutes and then toned for 15 to minutes inWater cc 300 Manganous sulfate gm 7 HCl (conc.) cc 4 The image is washedfor 5 minutes and converted to manganese dioxide by bathing for 10minutes in Water cc-.. 200 Sodium hydroxide gm 1 After washing for 5minutes, the image is fired at cone 09 similar to an underglaze ceramicpigment. The base is then glazed and refired at cone 06 to a brown-blackcolored image under the glaze.

Example VII The emulsion of Example I is coated on a porcelain plate anddried. By means of a photo-enlarger, a negative image is projected ontothis light-sensitive surface for an exposure time of fl6 for 10' to 30seconds. The resulting latent image is then developed for 1 minute at 18C. in

Distilled water cc 1000 Metol (p-methylaminophenol sulfate) gm 1 Sodiumsulfite gm 28 Hydroquinone gm 4 Sodium carbonate gm 21 Potassium bromidegm 1 After development, the plate is rinsed in Water for 30 seconds andthen fixed for 5 minutes in a 25 solution of sodium thiosulfate. Afterthe fixer has removed all undeveloped silver halide, the plate is washedin water for 5 minutes and then dried. The resulting silver positiveimage is then bleached for 15 minutes at 18 C. in

Distilled Water cc 1000 Glacial acetic acid cc 30 Lead nitrate gm 10Potassium ferricyanide gm 10 While in this solution, all of the silverimage bleaches out to form a yellow-white image of lead ferrocyanide.The yellowish image is then washed for 15 minutes during which time itbecomes colorless. The plate is then treated for 10 minutes at 18 C. in

Distilled Water cc 1000 Hydrochloric acid (98%) cc 10 Ferrous sulfate gm10 This solution causes the rapid formation of a deep purplish-bluepositive image consisting of ferrous ferrocyanide and the decomposedlead ferrocyanide yields a flux image of lead sulfate. After washing for5 minutes, the plate is dried and finally fired in a ceramic kiln tocone 014 to 013. This will normally require 1 to 3 hours, depending onthe particular kiln.

After cooling, the plate will contain a vitrified positive image that iscontained completely within the glaze. The decomposition of ferrousferrocyanide has resulted in a red-brown image and the decomposition ofthe lead sulfate has caused it to be fluxed to a glossy vitrifiedsurface.

Example VIII The procedure as given in Example VII may be followedexactly, but, in place of ferrous sulfate, the following metal salts maybe used either individually or in combinations.

Ferric sulfate Blue-white image. Copper sulfate Red-brown image.Manganous sulfate Blue-white image. Cobaltous sulfate Grey-green image.Nickel sulfate Yellow-green image. Uranium sulfate Reddish image.Van-adyl sulfate Yellow image. Stannous sulfate White image.

The use of these salts will result in the formation of metalferrocyanides as Well as :a lead sulfate flux.

Example IX The ceramic ware coated as in Example II is exposed to anegative by use of an are light for 3 minutes. This exposure causeshardening of the emulsion in the lightstruck areas. The non-light struckareas are swabbed with water or dilute acid to effect removal of theemulsion in the image areas. This produces a relief which may be firedat cone ()6 to produce a permanent positive colored i-ma-ge.

Modifications of the invention will occur to persons skilled in the artand I, therefore, do not intend to be limited in the patent grantedexcept as necessitated by the appended claims.

I claim:

1. A refractory surface coated with a gelatino-silver halide emulsioncapable of producing vitrified colored photographic images by subjectionto a vitrification process without causing the emulsion to contract,stretch, blister, tear, or frill, said emulsion containing a ratio ofsilver to gelatin ranging by weight from 3.75/1 to 1.25/1.

2. An article as defined in claim 1 in which the emulsion contains aceramic pigment.

3. An article as defined in claim 1 wherein the emulsion contains aceramic pigment and a flux.

4. An article as defined in claim 1 wherein the silver halide emulsionis a silver bromoiodide of the ammonia type.

5. A refractory surface coated with a photosensitive hydrophilicemulsion layer capable of being subjected to a vitrification processwithout causing the emulsion layer to contract, stretch, blister, tear,or frill, said emulsion layer comprising a colloidal carrier containinga radiation-sensitive compound, said colloidal carrier containing fromabout 10 to 50% of its 'weight of a polymer selected from the classconsisting of polyacrylamide, a copolymer of acrylamide with acrylicacid and mixtures of said polymer.

6. An article as defined in claim 5 wherein the radiationsensitivecompound is a silver halide.

7. An article as defined in claim 5 wherein the radiationsensitivecompound is a bichromate.

8. An article as defined in claim 5 wherein the emulsion contains aceramic pigment.

9. An article as defined in claim 5 wherein the emulsion contains aceramic pigment and a flux.

10. A method of producing permanent vitrified color images on arefractory surface which comprises exposing the article of claim 1 tolight underneath a pattern to form a latent image, developing and fixingsaid image to produce a silver image, bleaching the silver image with awater-soluble ferricyanide in the presence of a salt of a heavy basemetal, the oxide of which is a ceramic pigment, converting the resultingferrocyanide to the oxide and firing the oxide.

11. A method of producing permanent vitrified color images on arefractory surface which comprises exposing the article of claim 1 tolight underneath :a pattern to form a latent image, developing andfixing said image to produce a silver image, bleaching said silver imagewith a ferricyanide solution containing a salt of lead to produce a leadferrocyanide image, treating the image with an acid solution of asulfate of a heavy base metal to form .an image of the ferrocyanide ofthe heavy base metal and lead sulfate and firing the image.

12. A method of producing permanent vitrified color images on arefractory surface which comprises exposing the article of claim 6 tolight underneath a pattern to form a latent image, developing and fixingsaid image to produce a silver image, bleaching the silver image with awater-soluble ferricyanide in the presence of a salt of a heavy basemetal, the oxide of which is a ceramic pigment, converting the resultingferrocyanide to the oxide and firing the oxide.

13. A method of producing permanent vitrified images or a refractorysurface which comprises exposing the article of claim 6 to lightunderneath a pattern to form a latent image, developing and fixing saidimage to produce a silver image, bleaching said silver image with aferricyanide solution containing a salt of lead to produce a leadferrocyanide image, treating the image with an acid solution of asulfate of a heavy base metal to form an image of the ferrocyanide ofthe heavy base metal and lead sulfate and firing the image.

References Cited UNITED STATES PATENTS 2,607,683 8/1952- Yackel et a1.96-1l4 X 3,341,327 9/1967 Avery 96-34 2,900,255 8/ 1959 Charlton 96-343,171,742 3/1965 Yu 96-34 3,271,158 8/1966 Allentof et a1. 96-114 NORMANG. TORCHIN, Primary Examiner.

R. E. MARTIN, Assistant Examiner.

